1. Field of the Invention
The present invention relates to a cutter assembly and high volume submersible shredder pump. These are for reducing the size of solids within a liquid which is to be pumped by chopping, shredding, cutting or grinding.
2. Description of the Related Art
There is great commercial interest in centrifugal pumps which are capable of pumping liquids and slurries containing solid matter such as small pieces of disposed items. These pumps have the capability of chopping, shredding, cutting or grinding solid matter in the liquid mixture permitting the output from the pump to be disposed of more readily. Shredding pumps are used in liquid transfer applications that require size reduction for solid or semisolid materials contained in a liquid, in order to cut or shred such materials. The pump of the present invention includes an improved cutting assembly which is particularly useful when mounted to the suction side of submersible pumps that pump raw sewage, fish silage, byproducts of slaughter houses, waste water of paper mills and similar tough applications. These solid or semisolid materials are reduced in size such that a slurry is formed, which is more easily pumped than the solids themselves. These pumps have an inlet connected to a pumping chamber, and a driven shaft extending through the pumping chamber and into the inlet. The shaft rotates a cutting cylinder or disk in proximity to a plate cutter, thereby effecting the cutting action of the pump. Many other variations and configurations of grinder pumps are known, which provide shearing action between parts operating cooperatively at close tolerances. Examples of such pumps are disclosed in prior U.S. Pat. Nos. 3,650,081; 3,961,758; 4,108,386; 4,378,093; 4,454,993; 4,640,666; 4,697,746; 4,842,479; 5,016,825; 5,044,566; 5,256,032; 6,010,086; and 6,190,121.
U.S. Pat. No. 7,159,806 provides a cutting assembly for a grinder pump comprised of a rotary cutter rotatable against an opposing plate cutter. The cutting edges of the plate cutter include a plurality of V-slice cutting teeth, which create bridging spaces to pinch material which is being sucked in to ports and begin cutting along the V-slice and then for cut material to pass through and onward into the volute of the pump. The rotary cutter has a ground edge with a rake angle which shears the gathered material in cooperation with the cutting edges of the plate cutter. The grinder pump of U.S. Pat. No. 7,159,806 has an inner surface wall cover provided with a plurality of spiral grooves. These spiral grooves work cooperatively with the vanes of an impeller to outwardly eject any solid debris that begins to accumulate between the impeller vanes and wall. The impeller vanes of U.S. Pat. No. 7,159,806 are flat on the surface which meets the spiral grooves. The present invention improves on this prior design by employing cutting lobes having a grooved surface which mate with corresponding grooves of a circular plate cutter. As a result, many more cutting surfaces are provided which more effectively and quickly shred the solid materials within the liquid to be expelled. The inventive mechanism comprises a stationary perforated disc which is mounted to the suction casing of the pump and a shredder that is fastened to a rotating shaft; the interfacing of these two parts performs the actual shredding. The liquid moves freely thru the holes in the stationary plate and is readily pumped out. The solids that are larger than the holes in the stationary plate are immediately reduced in size by the rotating portion of the shredder mechanism.